1. Field of the Invention
The present invention relates to a dielectric device such as a dielectric duplexer consisting of a plurality of resonators arranged in parallel with each other, for use in mobile communication devices such as a mobile telephone, portable telephone and the like.
2. Description of the Related Art
A dielectric duplexer includes a plurality of resonators which are arranged in parallel with each other. An outer or grounding conductor covers the outer peripheral surface of the resonators except for an open end surface where through holes of the resonators open to the outside. The resonators are placed on a substrate which is provided with a coupling circuit for connection thereof. Such a dielectric duplexer is disclosed in Japanese Patent Provisional Publication No. 63-311801.
The dielectric duplexer has circuit elements such as a coupling capacitor for LC coupling between the respective resonators, which are mounted on a substrate, or conductors formed on the substrate for constituting a predetermined circuit. Such circuit elements or conductors are covered by a metal case which serves as a shielding case. The substrate is further provided with input/output electrodes for connection with external conductors. The duplexer is thus formed into a unit. Since the duplexer is formed into a unit in the above manner, its handling can be easier. Further, in such a structure, the coupling capacitor and the like are mounted on the substrate independently, so the circuit constant and the like can be set suitably and therefore good design freedom can be attained.
In the prior art structure, metallic terminal members which are fitted in the through holes of the respective resonators, are connected by way of lead wires to predetermined conductors formed on the substrate. Connection of the lead wires to the conductors is difficult and additional mounting of coupling capacitors on the substrate is necessitated, thus causing a problem in that the man-hours of labor required for assembly is increased and the circuit becomes imperfect, unsound or imprecise in design and fabrication, i.e., the design of the circuit becomes complicated. To solve such a problem, it has been proposed such a dielectric duplexer consisting of a dielectric resonator element and a multilayer circuit element which are connected to each other, as shown in FIGS. 9 and 10.
The dielectric duplexer shown in FIG. 9 consists of a dielectric resonator element a made up of a plurality of resonators b arranged in parallel, with each other and a multilayer circuit element c. Each resonator b has a connecting terminal d protruding from an open end thereof and electrically connected to an inner conductor. The connecting terminals d of the resonators b are disposed above the multilayer circuit element c and soldered to connection electrodes e formed on the upper surface of the multilayer circuit element c.
In such a structure, the multilayer circuit element c is required to be nearly half the thickness of the resonator element a so that the lower or bottom surfaces of the multilayer circuit element c and the resonator element a are flush with each other when the terminals d are connected to the electrodes e to allow the resonator element a and the circuit element c to be formed into an integral unit. This causes restrictions on the thickness of the multilayer circuit element c. As a result, there arises a possibility that by such a circuit element c an LC coupling circuit having an optimum capacitance and inductance cannot be attained. In case the bottom surfaces of the dielectric resonator element a and the circuit element b are not flush with each other, an unsound, unstable or unsecured condition of the resonator element a and/or the circuit element c may be realized at the time of their mounting onto a mounting circuit board, i.e., the resonator element a and/or the circuit element c cannot fit well on the mounting circuit board and therefore cannot be mounted thereon in a stable state.
The dielectric duplexer shown in FIG. 10 consists of a dielectric resonator element m made up of a plurality of resonators n arranged in parallel with each other and a multilayer circuit element p. The open end of the resonator element m is connected directly to the joining surface of the circuit element p so that the inner conductors o of the respective resonators n are connected to a conductor pattern (not shown) formed on the joining surface of the circuit element p.
In such a structure, the resonator element m and the circuit element p are adapted to be formed into a rectangular shape when joined together. To this end, the joining surface of the circuit element p and the open end of the resonator element m are required to have the same shape. Due to this, the joining surface of the circuit element p cannot be made larger as desired, thus causing a problem that, similarly to the structure of FIG. 9, the dielectric duplexer cannot attain an LC coupling circuit having an optimum capacitance and inductance. Further, in case the bottom surfaces of the resonator element m and the circuit element p are not flush with each other, an unsound, unstable or unsecured condition of the resonator element m and/or the circuit element p can result when the resonator element m and the circuit element p are mounted onto a mounting circuit board, i.e., the resonator element m and/or the circuit element p cannot fit well on the mounting circuit board and therefore cannot be mounted thereon in a stable state.
It is therefore an object of the present invention to provide a dielectric device which is free from the problems inherent in the prior art device.
It is another object of the present invention to provide a dielectric device of the foregoing character which is easy in assembling and simple in structure.
To achieve the foregoing objectives, there is provided according to an aspect of the present invention a dielectric device which comprises a dielectric resonator element having a plurality of coaxial resonators arranged in parallel with each other, the resonators having through holes provided with inner conductors, respectively, a multilayer circuit element having conductive patterns constituting a coupling circuit, the conductive patterns being laminated vertically while alternating with dielectric layers, the circuit element being rectangular and having a pair of first and second opposite vertical side surfaces extending along the longitudinal direction thereof, the coupling circuit having first connecting ends disposed at the first vertical side surface and second connecting ends disposed at the second vertical side surface, and a plurality of metallic terminal members electrically connecting between the inner conductors of the resonators and the first connecting ends of the coupling circuit.
According to another aspect of the present invention, there is provided a dielectric device which comprises a dielectric resonator element having a plurality of resonators arranged in parallel with each other, the resonators having through holes provided with inner conductors, respectively, a multilayer circuit element having conductive patterns constituting a coupling circuit, the conductive patterns being laminated vertically while alternating with dielectric layers, the circuit element being rectangular and having a pair of first and second opposite vertical side surfaces extending along the longitudinal direction thereof, the coupling circuit having first connecting ends disposed at the first vertical side surface and second connecting ends disposed at the second vertical side surface, a plurality of metallic terminal members electrically connecting between the inner conductors of the resonator element ad the first connecting ends of the coupling circuit, and a printed board mounting thereon the resonator element and the circuit element and having external connecting terminals electrically connected to the second connecting ends of the circuit element.
With the above structures, the resonator element and circuit element are electrically connected to each other by means of the metallic terminal members, so lead wires, wire bonding or the like is not necessitated. Thus, the dielectric device can be simple in structure while being capable of obtaining a neat or orderly appearance.
With the structure in which the resonator element and the circuit element are supported on the printed board, the dielectric device can have a single, planar bottom surface which is formed by the printed board, thus enabling the dielectric device to be mounted on a mounting circuit board stably without causing an unsound, unstable or unsecured condition thereof.
With the structure in which the circuit element whose conductive patterns are laminated vertically while alternating with dielectric layers, is electrically connected with the resonator element at one vertical side surface, so a variation of the horizontal area or extension of the circuit element does not cause any variation of the thickness of the circuit element and any obstacle in assembling. For this reason, the invented dielectric device does not have such restrictions on the shape that are otherwise caused by the prior art structures shown in FIGS. 9 and 10 thus making it possible to attain good design freedom and an LC coupling circuit having improved capacitance and inductance.